Use this template to bootstrap the creation of a container action. ๐
This template includes compilation support, tests, a validation workflow, publishing, and versioning guidance.
If you are new, there's also a simpler introduction in the Hello World Docker Action repository.
If you would like to use the GitHub Actions Toolkit in your container action, see the Container Toolkit Action repository.
To create your own action, you can use this repository as a template! Just follow the below instructions:
- Click the Use this template button at the top of the repository
- Select Create a new repository
- Select an owner and name for your new repository
- Click Create repository
- Clone your new repository
Important
Make sure to remove or update the CODEOWNERS
file! For
details on how to use this file, see
About code owners.
After you've cloned the repository to your local machine or codespace, you'll need to perform some initial setup steps before you can develop your action.
Note
You'll need to have a reasonably modern version of Docker handy (e.g. docker engine version 20 or later).
-
๐ ๏ธ Build the container
Make sure to replace
actions/container-action
with an appropriate label for your container.docker build -t actions/container-action .
-
โ Test the container
You can pass individual environment variables using the
--env
or-e
flag.$ docker run --env INPUT_WHO_TO_GREET="Mona Lisa Octocat" actions/container-action ::notice file=entrypoint.sh,line=7::Hello, Mona Lisa Octocat!
Or you can pass a file with environment variables using
--env-file
.$ cat ./.env.test INPUT_WHO_TO_GREET="Mona Lisa Octocat" $ docker run --env-file ./.env.test actions/container-action ::notice file=entrypoint.sh,line=7::Hello, Mona Lisa Octocat!
The action.yml
file defines metadata about your action, such as
input(s) and output(s). For details about this file, see
Metadata syntax for GitHub Actions.
When you copy this repository, update action.yml
with the name, description,
inputs, and outputs for your action.
In this template, the container action runs a shell script,
entrypoint.sh
, when the container is launched. Since you
can choose any base Docker image and language you like, you can change this to
suite your needs. There are a few main things to remember when writing code for
container actions:
-
Inputs are accessed using argument identifiers or environment variables (depending on what you set in your
action.yml
). For example, the first input to this action,who-to-greet
, can be accessed in the entrypoint script using the$INPUT_WHO_TO_GREET
environment variable.GREETING="Hello, $INPUT_WHO_TO_GREET!"
-
GitHub Actions supports a number of different workflow commands such as creating outputs, setting environment variables, and more. These are accomplished by writing to different
GITHUB_*
environment variables. For more information, see Workflow commands.Scenario Example Set environment vars echo "MY_VAR=my-value" >> "$GITHUB_ENV"
Set outputs echo "greeting=$GREETING" >> "$GITHUB_OUTPUT"
Prepend to PATH
echo "$HOME/.local/bin" >> "$GITHUB_PATH"
Set pre
/post
varsecho "MY_VAR=my-value" >> "$GITHUB_STATE"
Set step summary echo "{markdown}" >> "$GITHUB_STEP_SUMMARY"
You can write multiline strings using the following syntax:
{ echo "JSON_RESPONSE<<EOF" curl https://example.com echo "EOF" } >> "$GITHUB_ENV"
-
Make sure that the script being run is executable!
git add entrypoint.sh git update-index --chmod=+x entrypoint.sh
So, what are you waiting for? Go ahead and start customizing your action!
-
Create a new branch
git checkout -b releases/v1
-
Replace the contents of
entrypoint.sh
with your action code -
Build and test the container
docker build -t actions/container-action . docker run actions/container-action "Mona Lisa Octocat"
-
Commit your changes
git add . git commit -m "My first action is ready!"
-
Push them to your repository
git push -u origin releases/v1
-
Create a pull request and get feedback on your action
-
Merge the pull request into the
main
branch
Your action is now published! ๐
For information about versioning your action, see Versioning in the GitHub Actions toolkit.
You can now validate the action by referencing it in a workflow file. For
example, ci.yml
demonstrates how to reference an
action in the same repository.
steps:
- name: Checkout
id: checkout
uses: actions/checkout@v3
- name: Test Local Action
id: test-action
uses: ./
with:
who-to-greet: Mona Lisa Octocat
- name: Print Output
id: output
run: echo "${{ steps.test-action.outputs.greeting }}"
For example workflow runs, check out the Actions tab! ๐
After testing, you can create version tag(s) that developers can use to reference different stable versions of your action. For more information, see Versioning in the GitHub Actions toolkit.
To include the action in a workflow in another repository, you can use the
uses
syntax with the @
symbol to reference a specific branch, tag, or commit
hash.
steps:
- name: Checkout
id: checkout
uses: actions/checkout@v3
- name: Test Local Action
id: test-action
uses: actions/container-action@v1 # Commit with the `v1` tag
with:
who-to-greet: Mona Lisa Octocat
- name: Print Output
id: output
run: echo "${{ steps.test-action.outputs.greeting }}"